A lead-frame is a metal frame forming an extension line lead terminal with a die pad which is used for fixing a semiconductor pellet used in a plastic mold IC and a ceramics package IC. There is used for the metal frame, a lead-frame forming metal plate made of alloy mainly containing copper or copper-nickel as a material. In recent years, an element of an active metal series such as titanium and chromium has been added to the material as well. In any event, it is desired that the material used have good mechanical strength, high electric conductivity, high softening temperature, a coefficient of thermal expansion matching the coefficient of thermal expansion of a semiconductor pellet and a package material, secured flatness of a lead, small bending anisotropy, good heat releasing performance, and a low cost. A pattern is formed on the lead-forming metal plate by punching out or by etching with an etching solution. The punching out method can be carried out at a low cost and a precise pattern can be formed by the etching method.
In recent years, development in semiconductor and integrated circuit manufacturing accompanied with an increased demand for electronic parts using lead-frames has resulted in an increased requirement for providing lead-frame having uniform quality in large volume.
In manufacturing lead-frames, there has been used in the past, for example, an alloy plate mainly containing copper or an alloy plate mainly containing copper-nickel, and in order to remove rust preventives applied on the alloy plate, the alloy plate was subjected to a degrease treatment and an acid cleaning treatment. Then, a light-sensitive layer of a dry type film which is generally a negative type, is deposited or a liquid resist which is generally a negative type was coated, and dried on the plate to provide a light-sensitive material layer. After the light-sensitive layer was exposed through a prescribed etching pattern, it was then subjected to a developing treatment and any exposed parts of the light-sensitive layer were removed. Then, the alloy plate was dipped in an etching solution to form a prescribed etching pattern on the alloy plate surface.
For producing pattern-formed lead-frames with uniform quality in large volume by the use of a conventional lead-frame forming material as described above, a great many sheets of lead-frame forming materials have been prepared so far in the following manner: A great many sheets of metallic substrate, e.g., a great number of alloy plates as described above, are subjected to successive degreasing and acid cleaning treatments one after another in a batch treatment, thereby removing rust preventives coated on each sheet of the alloy plate, and each sheet of the thus treated alloy plate is coated with a light-sensitive material of a dry type which is generally a negative type by adhesion or deposition, or coated with a liquid resist which is generally a negative type by a coating method such as spin coating, each followed by drying, to provide a light-sensitive layer on the alloy plate.
The above-described conventional manners for preparing lead-frame forming materials have many problems as described below.
1. In the case of using a dry film, the preparation process is complicated. More specifically, the process comprises laminating a film on both surfaces of a resist, peeling off the film on one surface, adhering the bare surface of the resist to an alloy plate made of, e.g., copper, imagewise exposing the resist to light through the film on the other surface, peeling off the film on the resist surface, and developing the resist. In this process, the resist is frequently contaminated with dust upon adhesion of the dry film, thereby reducing to the yield. PA0 2. In the case of using a liquid resist, on the other hand, it is required that the resist be applied to both surfaces of every sheet of the plate by means of a rotary coating device such as spinner, thereby markedly deteriorating the productivity with an extremely great loss of the liquid resist, and further involving another serious problem of easy sticking of dust. PA0 3. After the degreasing and acid cleaning treatments as described above, a dry type film is adhered or deposited on both surfaces of the plate, and then the laminate is exposed to light with a mask film being placed on both the upper and lower surfaces thereof. If once fine dust is stuck on the dry film to be contacted with the mask film, it is not easy to eliminate the fine dust from the dry film. PA0 4. In the case of using a conventional dry film and liquid resist, the resist which is removed by development with a developer cannot be completely dissolved in the developer, but is partly released in the form of film. In some cases, there is a fear such that the resulting scum may reattach to the material to make it a rejected article. PA0 5. When a lead-frame forming material to which a conventional dry film or liquid resist has been adhered is allowed to stand for more than 3 or 4 days, the adhesion power becomes so strong that incomplete removal of the resist occurs, thereby making it impossible to form accurate patterns. PA0 6. Another problem arises when the etching pattern as described above is exposed to light. More specifically, a pattern formed mask film is placed on a lead-frame forming material on which a light-sensitive layer has been provided, and brought into close contact therewith. The close contact between the mask and the lead-frame forming material can be accomplished by various methods. For example, it can be squeezed by a roller on the mask film. Alternatively, the lead-frame forming material on which a mask film has been placed is set in a frame and then evacuated to remove the air between the mask film and the lead-frame forming material. Thus, it is tried to prevent a printing image from undercutting during exposure. However, in the roller squeezing method, it is hard to remove the air present between the mask film and the forming material. On the other hand, the evacuation method has a disadvantage in that it takes much time to remove the air from the central part because the air removal begins with the circumferential part, in the worst case, the air cannot be removed from the central part. PA0 7. The generation of pinholes and microscopic film peeling of the resist occasionally occur in the developing and etching steps. PA0 8. Still another problem is that it is difficult to realize a high resolution required as the market needs lead-frames with more pins and a higher precision. PA0 1. A lead-frame forming material which is prepared by coating a light-sensitive material on both surfaces of a metal web made of copper, copper alloy or nickel alloy, drying the coat, and winding it into a roll or cutting off at every fixed length and stacking thereof, wherein the light-sensitive material comprises (1) a diazo salt light-sensitive resin and (2) a water-insoluble but alkaline water-soluble lipophilic high molecular weight compound. PA0 2. A lead-frame forming material as described in item 1 above, wherein protrusions having a height from 0.5 .mu.m to 30 .mu.m are provided on the surface of the light-sensitive layer. PA0 3. A lead-frame forming material as described in item 1 above, wherein fine roughness from 0.05 .mu.m to 1 .mu.m is provided on the surface of the metal web made of copper, copper alloy or nickel alloy. PA0 4. A lead-frame forming material which is prepared by coating a light-sensitive material on both surfaces of a metal plate made of copper, copper alloy or nickel alloy, drying the coat, and winding it into a roll or cutting off at every fixed length and stacking thereof, wherein the light-sensitive material comprises a photodimeric light-sensitive composition. PA0 5. A lead-frame forming material as described in item 4 above, wherein protrusions having a height from 0.5 .mu.m to 30 .mu.m are provided on the surface of the light-sensitive layer. PA0 6. A lead-frame forming material as described in item 4 above, wherein fine roughness from 0.05 .mu.m to 1 .mu.m is provided on the surface of the metal web made of copper, copper alloy or nickel alloy. PA0 7. A lead-frame forming material which is prepared by coating a light-sensitive material on both surfaces of a metal plate made of copper, copper alloy or nickel alloy, drying the coat, and winding it into a roll or cutting off at every fixed length and stacking thereof, wherein the light-sensitive material is a negative resist composition which comprises (1) a water-insoluble but alkaline water-soluble resin, (2) a compound capable of generating an acid by irradiation with active rays or radiant rays, and (3) a compound containing at least one crosslinkable group by the action of an acid. PA0 8. A lead-frame forming material as described in item 7 above, wherein protrusions having a height from 0.5 .mu.m to 30 .mu.m are provided on the surface of the light-sensitive layer. PA0 9. A lead-frame forming material as described in item 7 above, wherein fine roughness from 0.05 .mu.m to 1 .mu.m is provided on the surface of the metal web made of copper, copper alloy or nickel alloy. PA0 (1) In the first embodiment of the present invention, the light-sensitive layer comprises a diazo salt light-sensitive resin and a water-insoluble but alkaline-soluble lipophilic high molecular weight compound. PA0 (1) Acrylamides, methacrylamides, acrylic esters, methacrylic esters and hydroxystyrenes containing aromatic hydroxyl group, such as N-(4-hydroxyphenyl)acrylamide, N-(4-hydroxyphenyl)methacrylamide, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxyphenyl methacrylate, m-hydroxyphenyl methacrylate, and p-hydroxyphenyl methacrylate; PA0 (2) Acrylic esters and methacrylic esters containing aliphatic hydroxyl group, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxybutyl methacrylate; PA0 (3) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride and itaconic acid; PA0 (4) (Substituted) alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, benzyl acrylate, 2-chloroethyl acrylate, glycidyl acrylate and N-dimethylaminoethyl acrylate; PA0 (5) (Substituted) alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, glycidyl methacrylate and N-dimethylamylethyl methacrylate; PA0 (6) Acrylamides or methacrylamides such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-ethylacrylamide, N-hexylmethacrylamide, N-cyclohexylacrylamide, N-hydroxyethylacrylamide, N-phenylacrylamide, N-nitrophenylacrylamide and N-ethyl-N-phenylacrylamide; PA0 (7) Vinyl ethers such as ethyl vinyl ether, 2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether and phenyl vinyl ether; PA0 (8) Vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate and vinyl benzoate; PA0 (9) Styrenes such as styrene, .alpha.-methylstyrene and chloromethylstyrene; PA0 (10) Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone and phenyl vinyl ketone; PA0 (11) Olefins such as ethylene, propylene, isobutylene, butadiene and isoprene; PA0 (12) Vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine, acrylonitrile and methacrylonitrile; PA0 (13) Unsaturated imides such as maleimide, N-acryloylamide, N-acetyl methacrylamide, N-propionyl methacrylamide and N-(p-chlorobenzoyl) methacrylamide; PA0 (14) Unsaturated sulfonamides such as methacrylic amide, e.g., N-(o-aminosulfonylphenyl)methacrylamide, N-(m-aminosulfonylphenyl)methacrylamide, N-(p-amino)sulfonylphenyl methacrylamide, N-(1-(3-aminosulfonyl)naphthyl) methacrylamide, N-(2-aminosulfonylethyl)methacrylamide, acrylamide containing the same substituents as above, and methacrylic ester, e.g., o-aminosulfonylphenyl methacrylate, m-aminosulfonylphenyl methacrylate, p-aminosulfonylphenyl methacrylate, 1-(3-aminosulfonylnaphthyl)methacrylate, and acrylic ester containing the same substituents as above; PA0 (15) Unsaturated monomers having crosslinkable groups in its side chains, such as N-(2-(methacryloyloxy)-ethyl)-2,3-dimethylmaleimide and vinyl cinnamate, which may be copolymerized with monomers copolymerizable with the above-mentioned monomers; PA0 (16) Phenolic resins as disclosed in U.S. Pat. No. 3,751,257 and polyvinyl acetal resins such as polyvinyl formal resin and polyvinyl butyral resin; and PA0 (17) High molecular weight compounds obtained by alkali-solubilizing polyurethane, as disclosed in JP-B-54-19773 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-57-94747, JP-A-60-182437, JP-A-62-58242, JP-A-62-123452, JP-A-62-123453, JP-A-63-113450, and JP-A-2-146042. PA0 (2) The light-sensitive composition to be used in the second embodiment of the present invention is a photodimeric light-sensitive composition. PA0 (3) The light-sensitive composition to be used in the third embodiment of the present invention has the following components:
In addition, the following new problems arise in the course of application of the material of the present invention.